From: Oliver Neukum <oliver@neukum.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: netdev@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH] net/usbnet: avoid recursive locking in usbnet_stop()
Date: Mon, 20 Feb 2012 17:21:38 +0100 [thread overview]
Message-ID: <201202201721.38136.oliver@neukum.org> (raw)
In-Reply-To: <20120220160148.GA7910@linutronix.de>
Am Montag, 20. Februar 2012, 17:01:48 schrieb Sebastian Andrzej Siewior:
> |kernel BUG at kernel/rtmutex.c:724!
> |[<c029599c>] (rt_spin_lock_slowlock+0x108/0x2bc) from [<c01c2330>] (defer_bh+0x1c/0xb4)
> |[<c01c2330>] (defer_bh+0x1c/0xb4) from [<c01c3afc>] (rx_complete+0x14c/0x194)
> |[<c01c3afc>] (rx_complete+0x14c/0x194) from [<c01cac88>] (usb_hcd_giveback_urb+0xa0/0xf0)
> |[<c01cac88>] (usb_hcd_giveback_urb+0xa0/0xf0) from [<c01e1ff4>] (musb_giveback+0x34/0x40)
> |[<c01e1ff4>] (musb_giveback+0x34/0x40) from [<c01e2b1c>] (musb_advance_schedule+0xb4/0x1c0)
> |[<c01e2b1c>] (musb_advance_schedule+0xb4/0x1c0) from [<c01e2ca8>] (musb_cleanup_urb.isra.9+0x80/0x8c)
> |[<c01e2ca8>] (musb_cleanup_urb.isra.9+0x80/0x8c) from [<c01e2ed0>] (musb_urb_dequeue+0xec/0x108)
> |[<c01e2ed0>] (musb_urb_dequeue+0xec/0x108) from [<c01cbb90>] (unlink1+0xbc/0xcc)
> |[<c01cbb90>] (unlink1+0xbc/0xcc) from [<c01cc2ec>] (usb_hcd_unlink_urb+0x54/0xa8)
> |[<c01cc2ec>] (usb_hcd_unlink_urb+0x54/0xa8) from [<c01c2a84>] (unlink_urbs.isra.17+0x2c/0x58)
> |[<c01c2a84>] (unlink_urbs.isra.17+0x2c/0x58) from [<c01c2b44>] (usbnet_terminate_urbs+0x94/0x10c)
> |[<c01c2b44>] (usbnet_terminate_urbs+0x94/0x10c) from [<c01c2d68>] (usbnet_stop+0x100/0x15c)
> |[<c01c2d68>] (usbnet_stop+0x100/0x15c) from [<c020f718>] (__dev_close_many+0x94/0xc8)
>
> defer_bh() takes the lok which is hold during unlink_urbs(). The safe
> walk suggest that the skb will be removed from the list and this is done
> by defer_bh() so it seems to be okay to drop the lock here.
I am afraid there's something wrong in the hcd driver. Async unlink must
be possible with a lock held. I cannot approve this patch.
Regards
Oliver
next prev parent reply other threads:[~2012-02-20 16:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-20 16:01 [PATCH] net/usbnet: avoid recursive locking in usbnet_stop() Sebastian Andrzej Siewior
2012-02-20 16:21 ` Oliver Neukum [this message]
[not found] ` <201202201721.38136.oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org>
2012-02-20 16:42 ` Sebastian Andrzej Siewior
[not found] ` <4F4277DD.3090204-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2012-02-20 20:31 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1202201524290.11040-100000-pYrvlCTfrz9XsRXLowluHWD2FQJk+8+b@public.gmane.org>
2012-02-20 21:02 ` Sebastian Andrzej Siewior
[not found] ` <4F42B4E4.5090100-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2012-02-20 21:40 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1202201638330.13111-100000-pYrvlCTfrz9XsRXLowluHWD2FQJk+8+b@public.gmane.org>
2012-02-22 19:45 ` [PATCH] usb/core: remove "always" from usb_unlink_urb() kernel doc entry Sebastian Andrzej Siewior
[not found] ` <20120222194510.GA6964-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2012-02-22 20:28 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1202221525210.1311-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2012-02-29 22:04 ` [PATCH v2] " Sebastian Andrzej Siewior
2012-03-05 21:25 ` [PATCH] net/usbnet: avoid recursive locking in usbnet_stop() Sebastian Andrzej Siewior
2012-03-05 21:40 ` David Miller
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